The Internet Protocol Multimedia Subsystem (IMS) is an architecture for enabling Internet Protocol (IP) multimedia services for both wireline and wireless devices. The IMS is designed to logically separate access layers from services layers, so client devices can utilize various IMS services regardless of through what means the client device is attached to an IP network. Thus, for example, a wireless communication device (WCD) may be able to access the same voice over IP (VoIP) services from both a code division multiple access (CDMA) wireless wide area network as well as an 802.11 wireless local area network (WLAN). Similarly, the IMS may allow a user of a WCD to be able to make use of the same services from their Digital Subscriber Line (DSL) or cable modem access network.
IMS signaling and call control are largely standardized around the Session Initiation Protocol (SIP), while multimedia bearer traffic typically uses the Real Time Protocol (RTP). The IMS also leverages other protocols developed by the Internet Engineering Task Force (IETF), such as the Session Description Protocol (SDP) and DIAMETER. These common protocols support applications including VoIP, push to talk (PTT), video over IP, gaming, audio and video streaming, and other multimedia services. Additionally, an IMS infrastructure may support instant messaging, presence, email and social networking applications.
Despite the operators of communication networks adopting the IMS architecture in principle, actual IMS deployments have been slow to emerge. This slowness is likely due to many factors, including the IMS protocols and applications still being under development, the overall cost and complexity of IMS deployment, and, perhaps most importantly, the fact that tens of millions of legacy client devices do not support IMS-based protocols.
Given the delays in IMS deployment, non-IMS versions of the services described above have been developed and deployed for various types of client devices. However, these non-IMS applications may not support the same variation of the protocols that are employed by the IMS. Thus, non-IMS applications may be non-compatible with the IMS and therefore unable to leverage the centralized services or advanced services of the IMS.
It may be a number of years before all client devices are shipped with IMS-compatible protocol stacks and IMS-compatible applications. However, operators may want to begin leveraging IMS soon, so that they can offer operator-controlled multimedia services to their subscribers. Thus, it is desirable for there to be a means to allow non-IMS multimedia services executing on client devices to be integrated into an IMS architecture.